Effects of Inoculation by Bradyrhizobium japonicum Strains on Nodulation, Nitrogen Fixation, and Yield of Soybean (Glycine max L. Merill) Varieties on Nitisols of Bako, Western Ethiopia

Abstract

A field experiment was conducted during the 2005/6 growing season to assess the effect of Bradyrhizobium japonicum strains on the performance of soybean varieties. The field experiment was conducted at Bako ATVET College, West Shoa, Ethiopia. Three varieties of soybean (Jalele, Cheri, and Ethio-Yugoslavia) and two strains of Bradyrhizobium japonicum (TAL 378 and TAL 379) along with one uninoculated treatment were laid out in a randomized complete block design with nine variety and strain combinations and three replications. Inoculated and uninoculated seeds of soybean were planted on prepared beds. All the nodulation parameters, namely, nodulation rating, nodule number per plant, nodule volume per plant, and nodule dry weight were significantly influenced by the main effect of Bradyrhizobium japonicum strains alone. The main effect of soybean variety did not affect these parameters significantly. The dry matter production and nitrogen uptake at midflowering were highly significantly () affected by the main effects of both variety and strain. The yield and the yield components such as number of pods per plant, number of seeds per pod, seed yield, thousand seed weight, above-ground dry biomass, and total nitrogen uptake were highly significantly () affected by inoculation of Bradyrhizobium strains alone. A yield increase of 53.2% was obtained due to inoculation of TAL 379 over the uninoculated control. The variety effect was also significant () on number of pods per plant, seed yield, thousand seed weight, harvest index, and total nitrogen uptake. Variety and Bradyrhizobium strain interaction was detected on number of nodules per plant and nodule dry weight.